One of the major drawbacks associated with many prior art vehicles and/or vehicle bumper assemblies arise from their respective inability to effectively and/or satisfactorily function and/or cooperate with the bumper support structure to dissipate energy generated in, or arising from an "offset" or angular collision. As used within this Application the term "bumper assembly" and "bumper system" means a bumper and its supporting structure.
This drawback is of a relatively high concern since such "offset" collisions are relatively common and the resulting structural deformation type "intrusion" into the passenger compartment can be severe. Particularly, such "offset" or angular type collisions occur when, for example, two vehicles angularly collide in a manner in which their respective longitudinal axis are "offset" or form an angle between zero degrees and one hundred and eighty degrees during or at the time of collision. Moreover, "offset" collisions also commonly occur when a vehicle impacts a stationary or fixed object such as a tree or an abutment at some angle with respect to the vehicle's longitudinal axis, between zero degrees and one hundred and eighty degrees, or if the impact "favors" (e.g. occurs) on only one side of the vehicle.
Conventional bumpers were originally designed to protect the vehicle during low speed collisions. Recently, safety concerns from consumers as well as new government regulations have mandated greater occupant safety which has required improved energy management that goes beyond that which is provided by the "basic" or "conventional" bumpers and/or bumper assemblies, which normally function to protect the vehicle from damage caused by low speed collisions.
The kinetic energy involved in a collision is directly proportional to the vehicle's mass multiplied by the square of the vehicle's speed. A bumper system and/or assembly which comprises at maximum about 10 inches of vehicle length can only absorb a collision in the 5 miles per hour range. However, such a bumper would be inadequate to absorb the energy generated in a 30 mile per hour collision which is about 36 times greater than that generated in a 5 mile per hour collision and which requires about 20 to 24 inches of crush to be fully absorbed.
A conventional bumper and/or bumper assembly typically absorbs the kinetic energy of a collision through deformation of a foam beam which is generally covered by a flexible polymer cover, or by the stroking of a shock absorber type device which is filled with a gel. At higher speeds, the energy involved in the collision increases, with the square of the velocity of the vehicle, and at speeds above 5 miles per hour, the vehicle bumper system is usually unable to absorb the added energy and the vehicle's frame structure, which supports the bumper, undergoes plastic deformation. It has been found that a closed tubular structure, generally rectangular for ease of manufacture, can be designed to collapse in a controlled manner. This tubular structure can be manipulated by pre-forming the tube to induce progressive buckling failure in a desired manner, or by changing physical characteristics of the tube such as tapering the tube, changing the wall thickness, or changing the numbers and/or types of comers (e.g. an octagonal tube). These alterations provide the desired force deflection characteristics for specific vehicles.
For example, the Volvo corporation has used a rectangular section bumper beam supported by rectangular frame beams to achieve a square wave deceleration pulse. In the Volvo design, the relatively strong bumper beam generally assures that the impact load is carried to the vehicle fore-aft beams for crash energy absorption. The energy absorbed by the vehicle's structure can be described as equal to the area under the vehicle's load versus deformation curve. It is desirable that a vehicle's fore-aft structure carry a high load over a long stroke to allow maximum energy dissipation. The higher the deceleration load, the less deformation will occur. The deceleration load must be balanced or injury may occur. If it is too high, the deceleration can result in a high deceleration force (measured in units referred to as "G's" or "g's" and having a value equal to the gravitational constant which is about 32 feet/sec.sup.2) on the occupant's chest and head; if the deceleration is too low, the result is a larger deformation to the vehicle which results in greater crushing to the occupant compartment.
The tubular structure's energy absorption is generally tailored to meet U.S. Government mandated standards which specifies a perpendicular impact into a barrier. Unfortunately, during "real world" collisions, the vehicle's structure can be loaded "off axis" or at an angle. With off-center or angular loads, the vehicle's structure tends to be loaded on one side only, and the loads on this portion of the structure tend to be non-axial. With non-axial loading the tubular structure tends to buckle quickly thereby reducing the energy absorption capability of the column and increasing the amount of intrusion into the passenger compartment. The combination of loading only half of the vehicle's structure, along with this structural buckling, results in much higher intrusion into the passenger compartment than would occur in a full frontal collision.
Conventional vehicle bumpers and/or bumper assemblies are generally adapted to absorb and/or dissipate the force and/or energy that is generated when a vehicle collides with or is impacted by another vehicle or object, thereby protecting the vehicle and its passengers and/or the contents of the vehicle from damage or injury.
For example and without limitation, conventional or typical automotive vehicles generally include a first bumper assembly located or mounted in or on the front of the vehicle and a second substantially identical bumper assembly located or mounted in or on the rear of the vehicle.
More particularly, conventional or typical bumpers and/or bumper assemblies usually comprise a generally "C" shaped or closed section metal bumper reinforcement or mounting member having a generally flat planar surface which is normally deployed perpendicular to the longitudinal axis of symmetry of the vehicle and which is positioned such that its planar surface faces toward the exterior of the vehicle. The bumper member usually has or includes a channel portion, longitudinally coextensive to the flat planar surface, such channel portion being normally connected to at least two substantially identical reinforcement beam members, each having a generally rectangular tubular shaped cross section and positioned within or attached to the channel of the bumper on opposed end portions, while being substantially parallel to the longitudinal axis of symmetry of the vehicle. Typical bumpers or bumper assemblies also generally include a substantially hollow bumper cover which is generally overlaid with a flexible material, such as plastic, and which is formed and painted to suit the style and shape of the vehicle. Additionally, in many vehicles, the bumper cover is often filled with a deformable, impact absorbing, foam type material, such as and without limitation conventional and commercially available urethane. The bumper cover is adapted to removably mount to the bumper member and the bumper member and cover cooperate to maintain or keep the deformable foam in a fixed position in order to allow the foam to absorb low speed collision type energy, thereby protecting the structural integrity of the vehicle.
Some of these prior vehicle bumpers and bumper assemblies are described, for example and without limitation, in U.S. Pat. No. 4,968,076 of Kenji and 4,826,226 of Klie et al., which are each fully and completely incorporated herein by reference, word for word and paragraph for paragraph. Further, vehicle bumpers are generally known to those of skill in the art and are set forth, for example and without limitation, within U.S. Pat. No. 4,350,378 of Wakamatsu and within U.S. Pat. No. 4,968,076 of Kuroki, each of which is fully and completely incorporated herein by reference, word for word and paragraph for paragraph.
One of the major drawbacks associated with many of these prior art vehicle bumpers and/or vehicle bumper assemblies arise from their respective inability to effectively and/or satisfactorily absorb and transfer energy generated in or arising from an "offset" or angular collision. This drawback is of a relatively high concern since such "offset" collisions are relatively common and can result in intrusions into the passenger compartment. Particularly, such "offset" or angular type collisions arise when, for example, two vehicles angularly collide in a manner in which their respective longitudinal axes are "offset" or form an angle between zero degrees and one hundred and eighty degrees during or at the time of collision. Moreover, "offset" collisions also commonly occur when a vehicle impacts a stationary or fixed object such as a tree or an abutment at some angle with respect to the vehicle's longitudinal axis, between zero degrees and one hundred and eighty degrees, or if the impact "favors" (e.g. occurs) on only one side of the vehicle.
These "offset" impact type collisions are known to particularly cause a relatively great amount of vehicle damage since the impact energy of an "offset" collision is generally absorbed only by the portion of the vehicle structure actually involved in the impact and/or by the portion of the vehicle very near the point of impact. Hence, in an "offset" type collision, the colliding vehicles are often-times crushed or deformed to a greater extent on the side or portion of the vehicle nearest the point of impact. This deformation often involves or results in a relatively large amount of structural damage, especially to the passenger compartment, and/or a relatively high amount of injury to any passenger riding within the passenger compartment. Thus, the risk or probability of death or serious bodily injury is dramatically increased if a collision is "offset", especially if the collision involves multiple passengers located in different areas of the passenger compartment.
The Applicant has found that differing methods of testing for offset crashes result in significantly different intrusion and deceleration. The U.S. government, in attempt to promote safer vehicles, has promulgated a test procedure covered by FMVSS208 (Federal Motor Vehicle Safety Standard). This procedure requires "full frontal" and "offset crash" testing both to be conducted at 30 miles per hour. These test procedures measure, through the use of crash dummies, occupant injury criterion including head injury criteria (HIC), chest "G's" and femur loads. To meet the regulations for a full frontal crash generally requires a front structure which crushes at approximately 20 G's. To achieve this 20 G's it is desirable for the structure of each side of the vehicle to have a controlled and dynamic collapse. A vehicle weighing 4000 pounds would require a dynamic crash force of approximately 20 times its weight, or about 80,000 pounds. This crush force would be split between the two sides evenly as 40,000 crush force per side of one vehicle. A uniform crush force, or a square wave pulse, results in a vehicle crush of about 20 to 25 inches during a frontal collision. If the front structure buckles, it loses the ability to carry a load and the crush distance becomes longer, potentially resulting in a greater intrusion into the passenger compartment. A front structure which comprises a "generally rectangular" closed section achieves a square wave pulse when collapsed axially. During an offset collision, this section is side loaded which causes the structure to buckle in bending resulting in greatly reduced energy absorption and an increased intrusion into the passenger compartment.
A typical FMVSS 208 offset crash is conducted by rotating the barrier face by a 30 degree angle or 60 degrees to the axis of the vehicle which is towed into the barrier. During the FMVSS 208 barrier crash the vehicle slides along the low friction barrier face and this results both in a lowered G force and in a reduced intrusion into the occupant compartment. The FMVSS 208 offset test has been criticized as inaccurately simulating "real world" offset collisions where the vehicles stick together and do not slide; in actual collisions the intrusion into the vehicle is greater. In France, offset tests similar to the U.S. FMVSS 208 are conducted, but with vertical strips on the barrier, causing the vehicle to stick to the barrier. This "sticky barrier" reduces sliding and results in both higher G loading and larger intrusions into the occupant compartment. The French contend that this test protocol better matches "real world" collisions where vehicles become enmeshed and do not slide. The Germans have conducted tests where vehicles impact a flat wall with only a portion of the vehicle actually contacting the wall. They contend that this test protocol better represents the majority of crashes which occur in the "real world." With the German test method as well as the French, the vehicle does not slide, but sticks to the target, and the support structure on the side of the impact absorbs the crash. When the vehicle does not slide, the crash is mainly absorbed by half of the vehicle structure. The offset force components load the structure, which tends to buckle, resulting in increased intrusion into the passenger compartment on the crashed side of the vehicle.
Based on these tests the Applicant has found that vehicles involved in "real world" "offset" type collisions would incur substantially less damage, substantially less deformation, and substantially less intrusion into the occupant compartment if they were equipped with a bumper assembly which was adapted to "slide" or move laterally with respect to, or in reference to, the collision object.
A sliding bumper system would reduce the rate of velocity change by: (1) deflecting the vehicle path to partly miss the object, and (2) assuring that the energy of the collision causes primarily axial loading which results in an axial collapse of the support structure. An axially loaded tubular structure will collapse in an efficient square force versus deflection wave, thus absorbing the maximum energy to further minimize the intrusion. A sliding bumper lowers the overall energy by deflecting the vehicle and loads the structure efficiently, thus greatly maximizing potential intrusion into the passenger compartment.
The Applicant has found that vehicles involved in "offset" type collisions incur substantially less damage and substantially less deformation when they have bumper assemblies which are adapted to "slide" or move laterally with respect to or in reference to the object with which they are colliding. The Applicant has further found that this "sliding action" allows a significant portion of the impact energy to be absorbed and/or dissipated and reduces the amount of crushing and/or structural damage to the vehicle structure. The Applicant has also found that such a reduction in the structural damage and such enhanced energy absorption also reduces the probability of occupant injury since such enhanced energy absorption reduces the amount of the force applied to the the amount of the force applied to the vehicle occupants due to sudden vehicle deceleration (e.g. often referred to as "deceleration force" or "g force") caused by a collision, and further reduces the probability of injury sustained due to the structural deformity of the passenger compartment.
The Applicant has found that in an "offset" collision, conventional vehicle bumpers and bumpers assemblies are unable to efficiently transfer impact type energy to portions of the vehicle outside of the immediate point of impact, or substantially deflect impact energy away from the vehicle and from the passenger compartment of the vehicle. This deficiency is at least in part due to the fact that the primary elements of many of these prior conventional vehicle bumper assemblies (e.g. the bumper reinforcement beam member, the bumper cover, and the underlying foam), while generally flexible and/or deformable, are rigidly interconnected and are not usually moveable with respect to each other or with respect to the vehicle. The rigid interconnection of the various previously delineated elements of these conventional bumper assemblies tends to limit the amount of "sliding action" which the vehicle experiences in an "offset" collision, thereby increasing the amount of deformation and "g-force loading" applied to the passengers.
There is therefore a need for a vehicle bumper and/or a vehicle bumper assembly which overcomes the various drawbacks of the prior art, such as and without limitation those which have been previously delineated; which provides enhanced energy absorption and dissipation characteristics; which provides enhanced passenger protection; and which substantially permits at least some of the components of the bumper assembly, made in accordance with the teachings of the preferred embodiment of the invention, to be deployed in a selectively moveable and slideable relationship, thereby greatly decreasing the amount of structural deformation and deceleration type force loading applied to the vehicle and its passengers when the vehicle is involved in an "offset" type collision. Applicant's invention addresses and overcomes some or all of these drawbacks associated with these prior vehicle bumpers and bumpers assemblies and provides a new and useful vehicle bumper assembly having improved impact energy absorption and "offset" crash characteristics.